The present invention relates to an improved slide gate or sliding closure unit for controlling the discharge of molten metal from an outlet nozzle of a metallurgical vessel, particularly a steel foundry ladle, the sliding closure unit being of the type including a stationary refractory plate having therethrough a discharge opening aligned with the outlet nozzle of the vessel, a stationary housing assembly for mounting the stationary refractory plate on the metallurgical vessel, a movable refractory plate having therethrough a discharge opening, the stationary and movable refractory plates having complementary, abutting relative sliding surfaces, a movable frame mounting the movable refractory plate for movement with respect to the stationary refractory plate to bring the discharge opening of the movable refractory plate into and out of alignment with the discharge opening of the stationary refractory plate, and means for pressing the movable refractory plate toward the stationary refractory plate to ensure sealing between the complementary, abutting relative sliding surfaces.
Typically, such pressing means is in the form of spring loaded rocking or pivotable levers having support or contact members which are urged against, for example, guide tracks of the movable frame, thereby urging the movable frame and movable refractory plate toward the stationary refractory plate. These types of arrangements are disclosed in DE-AS 1,299,804 with respect to a movable refractory plate which is movable rectilinearly and in DE-OS 22 12 312 with respect to a movable refractory plate which is mounted for rotary movement. In such arrangements, the levers are mounted to extend generally perpendicularly to the direction of movement of the movable refractory plate. Thus, these levers are mounted with the support or contact ends beneath the movable frame and with opposite, spring-loaded ends extending outwardly therefrom. As a result of this arrangement, the overall sliding closure unit is of a relatively cumbersome design requiring a substantially large amount of space which only rarely is available. A further disadvantage of this conventional arrangement is that the levers are mounted in a manner which does not provide adequate stability to withstand the pressures necessary to ensure tight sealing between the two refractory plates.
Additionally, Austrian Pat. No. 359,664 discloses a sliding closure unit having a rectilinearly movable frame guided on rollers between two rocker-type frames, each mounted to oscillate on a swing-out lever. Spring buffers and a cross brace are provided on free ends of the levers and, during clamping of the levers against a housing structure by means of snap closures, the spring buffers cause the movable refractory plate to be pressed sealingly against the stationary refractory plate. With this construction, the rocker-type frames provided externally of the movable frame result in a relatively wide and high overall structure. Additionally, the contact pressure by the spring buffers mounted on an end face of the unit is applied in an asymmetric and indirect fashion via the levers which are exposed to strong torsional forces.